The invention relates to a circuit grinding apparatus with high-pressure roller mill for the pressure comminution of granular material and with at least one integrated sifter, in which both aggregates are arranged within two fixed side face walls and an interlying turnably borne material-conveyor ring settable into rotation for an internal material circulation, in which the material inflow occurs through one or several openings in one or in both housing-face walls from the side and the material outflow occurs likewise laterally through one or more openings in the housing-face wall.
In the known grinding apparatuses of the above-mentioned type (DE-A-196 30 687, corresponding to U.S. Pat. No. 5,918,823 and DE-A-197 26 523, corresponding to U.S. Pat. No. 6,032,887) it is a matter of very compact circuit grinding apparatuses with a high-pressure roller mill or roller press for the pressure comminution or material-bed comminution of granular material, and with integrated an sifter. There the two rollers of the roller mill or roller press are housed in a housing consisting of two fixed, that is non-rotating, side face walls, between which there is arranged a rotatably borne material conveyor ring settable into rotation by a rotary drive for an internal material circulation. This rotatably borne material conveyance of the housing rotates at, for example, about 40 to 80% of the critical rotating rate, i.e., the ring takes along the mill- or press-discharge material (scabbing material), according to formation of the lifting elements in the conveyor ring, into the region near of the upper apex point of the ring, and allows this material to fall from above into the roller gap, whereby the internal material circulation comes about. Bucket mechanisms or other space-demanding conveying members for the transport of the mill- or press-discharge material to the mill- or pres-inflow are eliminated. With the rotating material conveying ring, therefore, in the least space and with low expenditure for machinery there is achieved a multiple internal material circulation with multiple pass material bed stressing of the material, in which also relatively high material circulation loads brought about, for example, by reduced roller press pressures, are to be managed.
For the achievement of high finenesses in the milling material, in the housing of the known circuit grinding apparatuses a static and/or dynamic sifter is integrated, and the sifting air laden with the milling material is drawn off and separated from the fine material fraction outside of the circuit grinding apparatus.
In the known circuit grinding apparatuses the two revolving annular gaps between the rotating material conveyor ring and the two fixed, i.e. non-rotatable, side face walls must be sealed off even in the case of a sub-pressure in the working space, if grinding material is to be prevented from. passing through these annular gaps to the outside. In consequence of the in practice large diameters or of the rotating material conveyor ring, on the order of magnitude of, for example, 8 to 10 meters, even at lower rotating rates there are high relative velocities between the rotating material conveyance ring and the fixed side face walls, so that effective annular seals with such a great diameter would wear out relatively rapidly.
Underlying the invention is the problem of further developing a circuit grinding apparatus of the type mentioned at the outset, so that seals between the fixed side face walls and the interlying material conveyance settable in rotation are no longer necessary.
It is characteristic for the circuit grinding apparatus of the invention that the two fixed side face walls are combined over a housing part, for example an annular housing part, that houses the rotatable material conveyance ring inside a housing tightly enclosing the entire working space of the circuit grinding apparatus. For the reception of milling material leakages that can emerge through the two annular gaps between the rotatable material conveyance ring and the fixed side face walls, the housing part has on its underside at least one grinding material leakage discharge element such as, for example, a collecting funnel, for the discharge or collecting of such grinding material leakages, which (leakages) can advantageously be recirculated into the grinding circuit. At any rate, in the circuit grinding apparatus according to the invention there are not required any seals between the fixed side face walls and the interlying turnably borne material conveyance ring.
So that at least one sifter integrated into the circuit grinding apparatus of the invention can be arranged above or below the roller mill, according to a special feature of the invention, in the working space of the circuit grinding apparatus, underneath the roller mill there can be arranged two static cascade sifters, lying about in mirror image to one another, and on the underside of the housing for the reception of grinding material leakages, there can also be arranged two grinding material leakage discharges, such as, for example, collecting funnels, for the reception of such leakages.
For the facilitation of its assembling, the fixed housing part encapsulating the rotatable material conveyance ring, in particular an annular housing part which simultaneously offers an optimal protection according to the work security guidelines, can be divided, in particular divided in half.